When manufacturing certain aircraft industrial parts it is desirable, due to the configuration of the part, to have holes cut and countersunk by a reverse feed operation. A standard industry drill for use in such an operation is a Cleco Quackenbush reverse feed drill. This drill is available from the Quackenbush Drill Company, a division of Dresser Industries.
This standard reverse feed Quackenbush drill has a feature that upon completion of a cutting stroke the drill automatically returns the spindle to the starting position, i.e., the beginning of the cutting stroke. The automatic return feature utilized in the Quackenbush drill, however, can only be set to a tolerance of plus or minus 1/16 of an inch (0.0625). In addition, when the automatic return is activated on the Quackenbush drill, the cutter immediately returns to the beginning of the cutting stroke and there is no dwell time for cutter clean up of the hole in the part at the end of the stroke and consequently, the cutter leaves marks on the part.
In the manufacture of diverse aircraft parts the desired tolerance is 0.01 inch and cutter marks may be undesirable and have to be removed in a secondary polishing or grinding step.